: The investigators state improving the efficiency and accuracy of DNA sequencing methods is essential to the success of the Human Genome Program. The instrumentation to be developed in this proposal will result in new forms of scanning-probe microscopy/optical spectroscopies (SPMOS) which will permit the topographical chemical mapping of DNA samples with unprecedented lateral and normal resolution. The microscope detects a change in signal intensity and in spectral wavelength as it approaches an emission site. Due to the higher strength of radiation in the near zone, and due to tip-induced effects, large signals are observed. Low resolution physical mapping has recently been improved due to fluorescence in situ hybridization (FISH) and the use of interphase chromosomes. They claim SPMOS should resolve neighboring markers much better than conventional optical methods. Effects to be studied for SPMOS include quenching, stimulated emission, and shifts in fluorescence due to the probe tip. In Phase II, optically induced repulsive forces in chromatin will be studied in order to attempt to physically improve marker separations by using the high energy density of evanescent waves and field enhancements due to artificial microstructures. The applicant intends to demonstrate physical mapping of gene markers on interphase chromosomes with specification of actual spatial coordinates at a resolution of 1-100kbp with a hybrid instrument that has both imaging zoom and spectroscopic zoom capabilities. During Phase I of this project the applicant will develop a hybrid scanning probe fiber optic scan head which will be mounted on a conventional microscope and its utility will be demonstrated by imaging fluorescently labelled probes on selected mouse and human chromosomes.